1. Field of the Invention
The present invention relates generally to a transmission and reception method in a communication system, and more particularly, to a method and apparatus for encoding control information, and transmitting and receiving the encoded control information.
2. Description of the Related Art
Broadcasting-communication services have entered the real era of digitalization, multi-channelization, broadband and high quality. With the recent prevalence of high-quality digital Television (TV) and an increase in the number of service subscribers of cable TV broadcasting, the widespread use of various digital broadcasting devices using wired/wireless communication networks has increased. A transmission scheme suitable for broadband transmission, and efficient encoding, transmission, and reception of control information required to receive broadcast data are important for providing reliable digital broadcasting services.
A typical example of a transmission scheme that is suitable for broadband transmission may include Orthogonal Frequency Division Multiplexing (OFDM). OFDM, which transmits data using multiple carriers, is a kind of Multi-Carrier Modulation (MCM) that converts a serial input symbol stream into parallel symbol streams and modulates each parallel symbol stream with multiple orthogonal subcarriers, i.e., multiple subcarrier channels, before transmission.
FIG. 1 illustrates a frame including control information in a conventional communication system.
Referring to FIG. 1, a frame 101 includes a preamble section 102, which includes preamble symbols 104, . . . , 105, and a data symbol section 103, which includes data symbols 106, . . . 107. The preamble section 102 is commonly used in a receiver to acquire time and frequency synchronization, synchronization for frame boundaries, etc. For these and other reasons, a transmitter of a communication system transmits the preamble section 102 before transmitting the data symbol section 103.
However, depending on the communication system, a preamble may also be used to carry signaling information as control information that is transmitted and received between the transmitter and the receiver.
FIG. 2 illustrates a configuration of an OFDM symbol carrying a preamble in a conventional communication system. More specifically, an OFDM preamble symbol illustrated in FIG. 2 is an OFDM symbol carrying a preamble. For ease of explanation, the OFDM preamble symbol will be referred to herein as an OFDM symbol.
Referring to FIG. 2, an OFDM symbol 201 includes a header 203, which is allocated to multiple subcarriers, and a coded signaling block 205 (hereinafter, merely referred to as a “coded block”). In the coded block 205, the signaling information is allocated to remaining subcarriers, which were not allocated to the header 203, i.e., NL1—Cells subcarriers represented by indexes of 1 to NL1—Cells.
The header 203 may be used to acquire synchronization in a receiver, and may include additional information, such as a modulation scheme and a code rate for the coded block 205. Herein, it is to be noted that other subcarriers of the OFDM symbol 201, which are additionally allocated for features of a pilot or the like, have been omitted for the convenience of description.
Assuming that the preamble 102 is embodied as the OFDM symbol 201, a receiver acquires synchronization of a frame, based on the header 203 of the preamble 102, obtains control information, such as a transmission method of the data symbols 103 and a length of the frame, from the coded block 205 of the signaling information, and then receives data from the data symbols 106, . . . , 107.
FIG. 3 illustrates a process of encoding and transmitting control information in a conventional communication system.
Referring to FIG. 3, a transmitter generates a coded block from signaling information provided as control information by applying a coding technique based on a proper error correction code, and then allocates NL1—Cells subcarriers available for transmitting the signaling information. More specifically, if signaling information to be transmitted is provided, a Forward Error Correction (FEC) encoder 301 generates a coded block by encoding the signaling information according to a predetermined coding scheme. A modulator 303 generates a modulation symbol by modulating the generated coded block according to a predetermined modulation scheme. Thereafter, a subcarrier mapper 305 maps the modulation symbol to the NL1—Cells subcarriers available for transmission of the modulation symbol, and a header inserter 307 generates an OFDM symbol, as illustrated in FIG. 2, by attaching a header to the mapped modulation symbol.
As described above, in the conventional communication system, a coded block is generated from signaling information and transmitted in an OFDM symbol. While it has been described that one coded block is generated from signaling information and transmitted in one OFDM symbol for convenience, the signaling information may also be transmitted in more than one OFDM symbol. In this case, the communication system should segment the signaling information into multiple coded blocks and transmit the multiple coded blocks in multiple OFDM symbols, which requires an efficient segmentation scheme, coding scheme, and transmission and reception scheme.